1. Field of the Invention
The present invention relates to an impression forming mechanism which is used for a testing apparatus for evaluating material characteristics of a sample by applying force to the surface of the sample with an indentor in order to form an impression thereon and a hardness testing apparatus comprising the above-described the impression forming mechanism.
2. Description of the Related Art
There is a hardness testing apparatus for evaluating material characteristics of a sample by applying force to the surface of the sample with an indentor in order to form an impression thereon.
FIG. 7 shows a force applying mechanism which is used for the above-described hardness testing apparatus.
In FIG. 7, a hardness testing apparatus 200 which is a so-called Rockwell hardness testing apparatus, comprises an impression forming mechanism 210 comprising weights 201, a loading arm 202, a cam 203, a force shaft 204, an indentor shaft 205, an indentor 206, or the like.
In the impression forming mechanism 210, the weights 201 having a predetermined weight are hung from an end of the loading arm 202. The end of the loading arm 202 moves down by the rotation of the cam 203. A predetermined force is applied to the force shaft 204. The force applied to the force shaft 204 is transmitted to the indentor 206 through the indentor shaft 205. An impression is formed on a sample mounted on a sample mounting member 207 by moving down the indentor 206.
A force applying control of the above force applying mechanism is carried out by hanging the weights 201 having a predetermined weight from the loading arm 202.
Further, a force applying control, for example, disclosed in the U.S. Pat. No. 5,616,857, is known. A force applied to a sample is measured by a load cell disposed on the axis which is the same as that of an indentor. The force applying control is carried out so that an actual force measured by the load cell will approximate to a set force on the basis of result of comparing the actual force data with the set force data.
Recently, it is necessary that measuring instruments and apparatus including the above-described hardness test apparatus should be small.
However, in the above-described hardness test apparatus, the loading arm 202 is disposed apart from the indentor 206. Because the principal part of the impression forming mechanism is disposed in the position which is higher than that of the indentor 206, there is a problem that the hardness testing apparatus is so difficult to be small in the height direction.
Further, in the force applying control carried out by using weights, there is a problem that it cannot be confirmed whether the force having a set value is applied to a sample while an impression is formed on the surface of the sample.
In the case of the force applying control carried out by using the load cell, although the force for forming an impression can be set to the set value approximately, the load cell is strained by applying the force thereto. As a result, there is a problem that a measurement error is caused in proportion to an amount of the strain. Because the load cell is precious relatively, a force applying mechanism which can carry out the force applying control cheaper and more precisely is required.
In order to solve the above-described problems, an object of the present invention is to provide an impression forming mechanism which can easily make a testing apparatus be small in a height direction and a hardness testing apparatus which is made to be small.
Another object of the present invention is to provide an impression forming mechanism which can carry out a force applying control cheaper and more precisely and a hardness testing apparatus which can carry out a force applying control cheaper and more precisely.
That is, in accordance with one aspect of the present invention, the impression forming mechanism which is used for a testing apparatus for measuring material characteristics of a sample by forming an impression with an indentor on a surface of the sample, comprises; a body part, an arm which is supported by the body part so as to be movable rotationally, for attaching the indentor to a free end portion thereof, and an arm rotating force applying part for applying a force to the arm in order to move a free end side of the arm rotationally and in order to apply a pressing force for forming an impression on the surface of the sample, wherein the arm rotating force applying part is attached to the body part below the arm.
According to the present invention, because the arm rotating force applying part for moving the free end side of the arm rotationally is disposed to the body part below the arm and the indentor is attached to the arm directly, the structure of the parts disposed above the indentor can be more simple than that of the mechanism in which the arm is disposed apart from the indentor and in which a part for operating the arm is disposed between them, according to the earlier development. The impression forming mechanism can make a testing apparatus be small in a height direction by attaching the impression forming mechanism to a hardness testing apparatus.
For example, the testing apparatus for measuring material characteristics of a sample by forming an impression with an indentor on a surface of the sample is a hardness testing apparatus for measuring a hardness of a sample, a testing apparatus for measuring an electric resistance of a sample when an impression is formed on the surf ace of the sample or the like. However, the testing apparatus is not limited to them. The all of apparatuses having an impression forming mechanism are included.
For example, the arm rotating force applying part is a motor for moving the arm rotationally by moving up and down a ball screw, a hydraulic device or a pneumatic one for moving the arm rotationally by moving up and down a piston, or the like. However, the arm rotating force applying part is not limited to them. Any device which can move the arm rotationally, may be used.
The impression forming mechanism may further comprise a rotating force transmitting member for transmitting the force generated by the arm rotating force applying part to the arm as a rotating force.
According to the present invention, in particular, the force generated by the arm rotating force applying part can be transmitted to the arm as a rotating force by the rotating force transmitting member completely.
For example, the arm rotating force applying part may be a rigid body or an elastic body like a plate spring.
The body part may contain a part of the arm rotating force applying part.
Because a part of the arm rotating force applying part is contained in the body part, the impression forming mechanism can be small.
The impression forming mechanism may further comprise an electric operating member, wherein the arm rotating force applying part applies a rotating force to the arm by operating the electric operating member.
Because the electric operating member applies the rotating force to the arm, the rotational movement of the arm can be controlled more precisely than the movement of the arm, which is carried out by weights and cam mechanism according to the earlier development.
In accordance with another aspect of the present invention, the impression forming mechanism which is used for a testing apparatus for measuring material characteristics of a sample by forming an impression with an indentor on a surface of the sample, comprises; a force applying part for applying a force in order to apply a pressing force for forming an impression on the surface of the sample to the indentor, a force transmitting member for transmitting the force applied by the force applying part to the indentor, which is deformed elastically by the force applied by the force applying part, a deformation measuring unit for measuring an amount of an elastic deformation of the force transmitting member by setting a predetermined reference position of a predetermined part thereof to a reference point, and a force applying control unit for controlling the force applied by the force applying part on the basis of the amount of the elastic deformation of the force transmitting member, which is measured by the deformation measuring unit.
According to the present invention, the force applied by the force applying part is transmitted to the indentor by the force transmitting member. At the same time, the force transmitting member is deformed elastically by the force. An amount of an elastic deformation of the force transmitting member is measured by the deformation measuring unit by setting the predetermined reference position of the predetermined part thereof to a reference point. Because the control of applying the force by the force applying part is carried out by the force applying control unit on the basis of the amount of the measured elastic deformation, it is possible not only that the force (load) for forming the impression becomes the set value approximately but also that the force applying control is carried out without the load cell. As a result, the force applying control can be carried out cheaper.
Further, because the loading arm is used and the force control is carried out on the basis of the displacement of the force transmitting member, it is not necessary that the compensating control which must be carried out when the force control is carried out by using the load cell because of the structural defect of the load cell, in which an amount of an indentation (that is, a hardness of a sample) includes an amount of a strain of the load cell, is carried out. As a result, an amount of an indentation of the indentor can be measured precisely. The above method is effective, in particular when an amount of an indentation of the indentor is measured dynamically and a hardness of a sample is calculated.
For example, the testing apparatus for measuring material characteristics of a sample by forming an impression with an indentor on a surface of the sample is a hardness testing apparatus for measuring a hardness of a sample, a testing apparatus for measuring an electric resistance of a sample when an impression is formed on the surface of the sample or the like. However, the testing apparatus is not limited to them. The all of apparatuses having an impression forming mechanism are included.
For example, the force applying part is a motor for moving the arm rotationally by moving up and down a ball screw, a hydraulic device or a pneumatic one for moving the arm rotationally by moving up and down a piston, or the like. However, the force applying part is not limited to them. Any device which can move the arm rotationally, may be used.
For example, the force applying part is an elastic body like a spring, a rubber or the like.
Although a linear scale, a capacitance displacement transducer, an LVDT (a linear variable differential transformer), an electric micrometer or the like is used in the deformation measuring unit, the present invention is not limited to them. Any unit which can measure an amount of the elastic deformation of the force applying part, may be used.
In the force applying control which is carried out on the basis of the amount of the elastic deformation of the force transmitting member, which is measured by the deformation measuring unit, for example, an amount of the measured elastic deformation is compared with a reference amount of the elastic deformation, which is previously set, and then the control is carried out on the basis of result of the above comparison, or the like.
The predetermined reference position may be a position in an initial condition in which the force transmitting member is not deformed elastically, or may be an optional position in a condition in which the force transmitting member is deformed elastically.
The control of the force applied by the force applying part may be a closed loop control.
According to the present invention, in particular, because the control of the force applied by the force applying part is carried out in a closed loop, the force applying control is always carried out. As a result, the force for forming the impression can become the set force more approximately.
The force transmitting member may be a spring body.
According to the present invention, because the force transmitting member is a spring body, the spring body and the deformation measuring unit can obtain the effect which is the same as the load cell. As a result, the force control can be carried out precisely. The impression forming mechanism is manufactured cheaper.
The spring body is a plate spring, a rod spring, a helical spring or the like.
In accordance with another aspect of the present invention, the hardness testing apparatus comprises; a body part, an arm which is supported by the body part so as to be movable rotationally, for attaching an indentor to a free end portion thereof, an arm rotating force applying part for applying a force to the arm in order to move a free end side of the arm rotationally and in order to apply a pressing force for forming an impression on a surface of a sample, and a hardness calculating mechanism part for measuring a shape of an impression formed on the surface of the sample, and for calculating a hardness of the sample on the basis of a result of measuring the shape of the impression, wherein the arm rotating force applying part is attached to the body part below the arm.
According to the present invention, the hardness testing apparatus can be small by applying the above impression forming mechanism.
For example, the hardness calculating mechanism part may be a device for calculating a hardness of the sample on the basis of the depth of the impression, or a device for calculating a hardness of the sample on the basis of the size of the indentation formed by the indentor. However, the hardness calculating mechanism part is not limited to them. Any hardness calculating mechanism part which can measure the hardness of the sample, may be used.
The hardness calculating mechanism part is, for example, a Rockwell hardness testing apparatus, a Vickers hardness testing apparatus or the like.
The hardness testing apparatus may further comprise a rotating force transmitting member for transmitting the force generated by the arm rotating force applying part to the arm as a rotating force.
The body part may contain a part of the arm rotating force applying part.
The hardness testing apparatus may further comprise an electric operating member, wherein the arm rotating force applying part applies a rotating force to the arm by operating the electric operating member.
In accordance with another aspect of the present invention, the hardness testing apparatus comprises; a force applying part for applying a force in order to apply a pressing force for forming an impression on a surface of a sample to an indentor, a force transmitting member for transmitting the force applied by the force applying part to the indentor, which is deformed elastically by the force applied by the force applying part, a deformation measuring unit for measuring an amount of an elastic deformation of the force transmitting member by setting a predetermined reference position of a predetermined part thereof to a reference point, a force applying control unit for controlling the force applied by the force applying part on the basis of the amount of the elastic deformation of the force transmitting member, which is measured by the deformation measuring unit, and a hardness calculating mechanism part for measuring a shape of the impression formed on the surface of the sample, and for calculating a hardness of the sample on the basis of a result of measuring the shape of the impression.
According to the present invention, it is possible to provide the precise and cheap hardness testing apparatus by comprising the above impression forming mechanism.
For example, the hardness calculating mechanism part may be a device for calculating a hardness of the sample on the basis of the depth of the impression, or a device for calculating a hardness of the sample on the basis of the size of the indentation formed by the indentor. However, the hardness calculating mechanism part is not limited to them. Any hardness calculating mechanism part which can measure the hardness of the sample, may be used.
The hardness calculating mechanism part is, for example, a Rockwell hardness testing apparatus, a Vickers hardness testing apparatus or the like.
The control of the force applied by the force applying part may be a closed loop control.
The force transmitting member may be a spring body.
In accordance with another aspect of the present invention, the impression forming mechanism comprises; an arm with an indentor for forming an impression on a surface of a sample, and an arm operating part for operating the arm in order to apply a force to the sample, wherein the arm operating part is disposed below the arm.
The arm operating part may apply a rotational force to the arm in order to move the arm rotationally around a fixed end of the arm.
The impression forming mechanism may further comprise a motor for operating the arm operating part.
In accordance with another aspect of the present invention, the impression forming mechanism comprises; an elastic body for storing a force for forming an impression on a surface of a sample, a deformation measuring member for measuring an amount of a deformation of the elastic body, and a force control unit for controlling the force stored in the elastic body on the basis of measuring the amount of the deformation of the elastic body.
The force control unit may comprises a closed loop system for controlling the force stored in the elastic body in a closed loop.